The present invention generally pertains to transmission control systems and methods of controlling transmissions. More specifically, the present invention pertains to transmission control systems and methods which concurrently control multiple transmissions. In a more specific embodiment, the present invention pertains to multi-function control levers and methods in which a single operator actuated control lever controls two hydrostatic transmissions in a synchronized manner. The present invention can be used, for example, with a walk-behind, self-propelled lawn mower.
Motorized vehicles generally include a transmission which transmits engine power to drive wheels for propelling the vehicle. For example, existing zero turn radius walk-behind lawn mowers typically include dual hydrostatic drives powered by an engine to drive two drive wheels. Each hydrostatic drive drives a single drive wheel.
Each hydrostatic drive typically includes a hydrostatic pump connected to a hydrostatic motor by hydraulic lines. Accordingly, the zero radius turn lawn mowers have two separate hydrostatic pumps connected to two separate hydrostatic motors through a complex system of high pressure hoses, oil filters, cooling reservoirs and various interconnecting hydraulic lines. Each of the hydrostatic drives is controlled by operator controls.
The operator controls for each hydrostatic drive are separate control systems. In other words, there are two sets of operator controls, one set of operator controls for each of the hydrostatic drives and associated drive wheel. The operator controls for each hydrostatic drive include separate drive and neutral controls for each hydrostatic pump and a separate brake lever for each hydrostatic drive. Accordingly, there are numerous separate hand operated controls for the drive, neutral, and brake lock functions of the hydrostatic drives. The numerous controls require substantial experience for the operator to operate the drive systems and thus operate the lawn mowers. It can be quite difficult for operators to operate the equipment efficiently and skillfully. For example, the operator has to actuate separate controls for the two hydrostatic drives to place both hydrostatic drives in a desired mode, such as a drive mode, a neutral mode, or a brake mode.
Furthermore, numerous hydraulic components, such as hydraulic hoses and fittings, are required for the separate hydrostatic drives. The numerous hydraulic components can be subject to leaks and high maintenance. Additionally, manufacturing costs are relatively high because of the numerous hydraulic components.